Field-effect tunable epsilon-near-zero absorber
a field effect and absorber technology, applied in the field of epsilon-near-zero absorbers, can solve the problems of high optical loss, high optical loss, complex and expensive technology, etc., and achieve the effect of high absorption and high absorption levels
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example 1
[0053]The p-polarized (TM) light absorptance as a function of the incidence angle and ITO thickness and wavelength are shown in these FIGS. 2A-2F. The absorptance is calculated using IMD software. The optical properties of the ITO are modelled using a free electron Drude model. An intensity scale bar is on the right of several figures.
[0054]FIG. 2A is a schematic graph of the absorptance of the ENZ multilayer stack example shown in FIG. 1A due to the p-polarized (TM) excitation of the radiative Berreman mode for variable thicknesses compared to variable incidence angles at a fixed excitation wavelength. For example, carrier concentrations of the ITO nanolayers are N1=1×1021 cm−3, N2=8×1020 cm−3, N3=6.1×1020 cm−3, and N4=4.9×1020 cm−3. The absorptance is attributed to the excitation of the radiative Berreman mode for the structure. The excitation wavelength is fixed at 1020 nm as an example. The graph shows that the highest absorption can be achieved with the ITO thickness between ab...
example 2
[0064]FIG. 4A is a schematic diagram of a metal-oxide-semiconductor (MOS) structure example having an ENZ layer that is field-effect tunable. The tunable absorption can be enabled by the field-effect. The MOS configuration can be similar to an electronic field-effect transistor with a TCO. Electron accumulation occurs in the TCO at the TCO-insulator interface, when a bias is applied between the metal and TCO. The electron accumulation modifies the complex dielectric constant of the TCO. Electron accumulation increases plasma and ENZ frequency and therefore leads to a blue shift of the absorption peak in wavelength. A commercial device simulator that self-consistently solves the Poisson and drift-diffusion equations was used to calculate electron distribution in the MOS device.
[0065]FIG. 4B is a schematic graph of a spatial distribution example of an electron concentration N for different applied voltages across the ENZ layer shown in FIG. 4A. The exemplary MOS device includes a meta...
example 3
[0068]FIG. 6A is a schematic graph of measured absorptance versus wavelengths for a single layer with a high index material at an initial incidence with a light in the structure of FIG. 1B. An experiment was made of absorptance and dispersion of ultrathin Berreman and ENZ absorbers.
[0069]FIG. 6B is a schematic graph of measured and simulated dispersion characteristics of the Berreman mode in a 15 nm thin ITO nanolayer.
[0070]The ITO films were grown by radio frequency (RF) magneton sputtering on silica substrates. The sputtering temperature and process pressure were 400° C. and 5 mTorr, respectively. The RF power was 50 W and Ar flow rate was 40 sccm.
[0071]To measure the absorptance of the samples, linearly polarized and collimated light from a supercontinuum (SC) laser having a broadband wavelength range of 600-1700 nm was incident to the ITO nanolayer by means of a GGG coupling prism in the Kretschmann-Raether configuration, such as shown in FIG. 10. The coupling prism and a test s...
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